1. Field of the Invention
The present invention relates to methods that can be used to certify, i.e. to authenticate the messages transmitted by means of telecopiers or facsimile machines on telephone lines of the dial network. It also relates to devices enabling this method to be implemented.
2. Description of the Prior Art
Facsimile transmission is a method that is becoming increasingly widespread and enables the contents of a sheet containing textual material, both typewritten and handwritten material and even figures, to be transmitted from one place to another anywhere in the world by using the dial telephone or public telephone network. This method, which is also known as telefax (or fax for short) consists in analyzing the surface of the sheet that is sent, according to a system of scanning that is similar to a television scanning, and in transmitting the contents of the scanned lines dot by dot in encoding the luminous value of each dot. Roughly speaking, it may be said that a dot with a value of zero corresponds to a white dot and a dot with a value of 1 corresponds to a black dot. At reception, this scanning is reproduced, with the values of the dots, on a sensitive paper which therefore restores an exact image of the original, apart from the grid-related errors.
Since this method enables the transmission of signatures, it might be thought that a document transmitted by this method is sufficiently authentic in legal terms. This is not yet the case for it is, in fact, likened to a photocopy which, as is known, cannot be taken into account in a court of law. Its legal value by itself is insufficient. Besides, the only proof that the sender has of reception consists of the brief contents of a short acknowledgment of receipt, indicating that the copy has undoubtedly been received somewhere, in principle at a place corresponding to the number indicated at the top of the fax.
It is known, on the contrary, that a telex document has far greater legal authenticity and is fully accepted by the courts as a means of proof for both the sender and the receiver. Unfortunately, telex transmission is subject to major limitations. It can be used to transmit only texts using capital letters with a reduced number of punctuation signs, and has no graphic capacity. Besides, telex subscription rates are relatively steep, and it is furthermore necessary to have a particular machine available which cannot be used appropriately except by relatively specialized staff.
There is therefore a major need to make it possible to obtain the same legal authenticity for facsimile documents as for documents sent by telex while at the same time, naturally, enjoying the particular advantages that the fax method has over the telex method.